Speaker’s arguments for ordinary writing (5)
I believe the answer is:
prose
'ordinary writing' is the definition.
(I've seen this before)
'speaker's arguments' is the wordplay.
'speaker's' indicates a 'sounds like' (homophone) clue.
'arguments' becomes 'pros' (pro is a kind of argument).
'pros' is a homophone of 'PROSE'.
'for' is the link.
(Other definitions for prose that I've seen before include "Ordinary writing" , "Normal written language" , "Literary genre" , "Ropes (anag.)" , "Gossipy talker" .)